The present invention relates to the field of user control apparatus for generating command signals to control each of a plurality of functions of a system in two opposite senses.
There are many systems in which functions or properties of the systems are controlled in response to a user's operation of switches. For example, in a television receiver pairs of switches may be provided to increase and decrease the channel number of the channel to which the receiver is tuned, the volume level of the receiver and certain picture properties of the receiver such as brightness, contrast, color saturation and color tint. The arrangement least confusing to a user employs two switches for each function, i.e., an "up" switch for increasing the function and a "down" switch for decreasing the function. In mathematical terms, this arrangement requires 2 N switches, where N is equal to the number of functions to be controlled.
To reduce the cost and increase the reliability of the systems employing switches to control analog functions, arrangements which employ less than 2 N switches are desired. One prior arrangement for reducing the number of required switches includes a single common "up" switch, a single common "down" switch, and one function selection switch for each of functions to be controlled. In mathematical terms, this arrangement requires 2+N switches. The number of required switches may be further reduced by deleting one of the function switches if apparatus is provided for automatically enabling the up and down switches to be used to control the function associated with the deleted switch at a predetermined time delay after one of the other functions has been controlled. The resulting arrangement requires 2+(N-1) or 1+N switches.
While the arrangements described above reduce the number of switches required, they tend to be more confusing to the user than the arrangement with an "up" and "down" for each function.